Experts now say the disease develops for years before symptoms show

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En español | New guidelines for diagnosing Alzheimer's disease, published Tuesday by the National Institute on Aging and the Alzheimer's Association, set forth methods for identifying the disease before it progresses to full-blown dementia, and for the first time include lab and brain-imaging tests that can help identify Alzheimer's as the likely cause of a person's mental decline.

So far, though, there are no therapies that alter the devastating course of Alzheimer's disease. And in a media briefing Monday, authors of the new diagnosis guidelines emphasized that while testing for Alzheimer's pathology in the brain may one day be used to identify the disease at much earlier stages, today the tests are primarily a research tool. They are not ready for routine use in doctors' offices.

Lab and imaging test can help identify Alzheimer's. — plainpicture/Corbis

Delaying disability

Even so, Gary Kennedy, M.D., director of geriatric psychiatry at Montefiore Medical Center in New York, who was not on the guidelines panel, says he hopes the new diagnostic criteria encourage people with worrisome memory problems to seek help. Kennedy says there's a lot patients and their families can do to minimize the impact of Alzheimer's, from structuring the patient's environment to optimizing medical care, exercise and diet. "We need to think of dementia as a chronic condition," he says. "We can't really modify the disease, but we can push back the disability."

New tests outlined in the guidelines involve looking at the brain with imaging technologies like magnetic resonance imaging (MRI) and positron emission tomography (PET), and examining the fluid obtained by a spinal tap. The imaging studies can reveal so-called plaques made up of a protein called amyloid, a defining feature of Alzheimer's. They also can indicate characteristic patterns of shrinkage or reduced metabolic activity in the brain. The cerebrospinal fluid tests look for levels of amyloid as well as of another protein, tau, which makes up the twisted strands or "tangles" that, like plaques, are a signature brain pathology in Alzheimer's.

Weaknesses of the tests

Research studies have demonstrated that all these tests can help identify Alzheimer's as the cause of a patient's dementia, and can help predict which patients with milder symptoms will go on to develop dementia. But the tests aren't conclusive in themselves. They aren't standardized so that a certain result means the same thing in every medical center. And there's no clear cutoff separating normal findings from those indicating a problem. In addition, they're not available from most primary care doctors.